Hyperbolic Geometry of Superstring Perturbation Theory

Abstract: We explore the hyperbolic structure of the RNS formulation of perturbative superstring theory. The aim is to provide a systematic method to explicitly compute on-shell and off-shell closed superstring amplitudes with an arbitrary number of external states and loops. Using hyperbolic geometry, we construct gluing-compatible off-shell string measures by giving a set of gluing-compatible local coordinates around external punctures and a gluing-compatible distribution of picture-changing operators. These amplitudes satisfy the required off-shell factorization property. This provides a formalism within which string-theory amplitudes can be computed explicitly once the corresponding string measures are expressed in terms of certain coordinates on Teichm\"uller space, the so-called Fenchel-Nielsen coordinates.